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Old 14th September 2006, 03:07 PM   #1
Molloy is offline Molloy  Europe
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Default 6as7 SRPP output stage

Hi,

I am trying to build this amp:

http://www.diyaudio.com/forums/attac...mp=1037816258&


Problem is i don't want to use the 6110 tube, a miniature one and difficult for me to locate. I have the 6av6 whose triode looks very much like a 12ax7.

I have a 6dj8 and a 5965...which do you think is best to substitute the 6110? Will have to change some resistor values?
Hell, this Morin liked weird tubes.
He says sound is as good as in any 2a3,300B amp plus the amp isn't expensive... those big resistors inthe 6as7 cathodes will cost me more than the output trafo.

The 6as7 in SRPP sounds good, i know because i have tried but with a differnt driver and less current; i have read that it is because the 6as7 in srpp behaves as a current amplifier and that makes the tube pretty much neutral in sonics....


Can somebody help, 5965 or 6dj8 for the 61110?
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Old 14th September 2006, 03:22 PM   #2
Molloy is offline Molloy  Europe
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Sorry the link doesnt work.
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Old 14th September 2006, 04:05 PM   #3
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I suggest the 5965 as it has a 200V H-K rating that is needed for the srpp stage.
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Old 14th September 2006, 07:21 PM   #4
rdf is offline rdf  Canada
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Default Re: 6as7 SRPP output stage

Quote:
Originally posted by Molloy
Hi,

The 6as7 in SRPP sounds good, i know because i have tried but with a differnt driver and less current; i have read that it is because the 6as7 in srpp behaves as a current amplifier and that makes the tube pretty much neutral in sonics....

Hi Molloy. It might be worth reading over John Broskie's analysis of cathode followers on http://www.tubecad.com. He goes to great pains to differentiate between between a stage's low output impedance and its ability to drive current. As I understand it, the reason a 6as7 works well is because it can drive current. I suspect a 6V6 will bomb looking into that 600 ohm load.

Edit: BTW, who is that in your avatar?
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Old 15th September 2006, 05:39 PM   #5
Molloy is offline Molloy  Europe
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Hi RDF,

I like reading John Broskie but i don't get much of what he says...
only the witty parts :-)

As i am a bit inept in science i just try to trust my ears (not always reliable) and i do experiment with many circuits. His Aikido preamp is very good, i have build it.
There's sure a good reason why the 6as7 sounds so good in SRPP but i really don't know why. The only thing i know is that in a normal SE amp the 6as7 sounded only ok so i had to try something different.
Why certain amps sound so much better than others with the same parts is something i'll never understand that's why i like diy audio so much. It's full of surprises.
Just one example, yesterday i changed all resistors in a 2a3 amp i made. The amp sounded really good but i found these NOS carbon composition resistor in an old audio store and i had to try. Now the amp sounds much worse. Warmth is gone. Why? I have no idea but i know that i have to put the normal cheap carbon resistors back.

The man in the avatar is Samuel Beckett.

Oh, and i've changed my mind about the driver stage so i don't need help anymore. Gonna build this:

http://www.fva.is/%7Eflemming/hsakram/int-srpp-amp/int-12sn7-6sl7-srpp.pdf
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